The invention relates to an adjust pin for connecting a plurality of blocks of a wrist watch band with each other in a chain like shape, a method of manufacturing the same, and a wrist watch band connection structure using the plurality of the blocks.
As is generally known, a wrist watch is provided with a band so as to be worn on the wrist and so forth of a user. A tanned skin, for example, cattle, alligator, etc., cut in a strap-like shape, stitched together with a leather of different quality, overlaid thereon, for reinforcement, is generally used for the band of the wrist watch.
Also, there is available another wrist watch band called a metal band, made up of metal blocks, etc., connected together in a chain-like shape using pins called adjust pins, so that the blocks connected in a strap-like shape can be bent around the shape of the arm of a user. Additionally, there has recently become available yet another wrist watch band called a plastic band formed of a synthetic resin such as urethane, and so forth in a strap-like shape.
Either of these wrist watch bands is generally made up of two pieces of strap-like members, and one end of the respective strap-like members is connected with a body of a wrist watch, including a display part, while the other end thereof is connected with each other by means of a catch or the like.
When the wrist watch is worn on the wrist of a user, the wrist watch is placed on the wrist, and the two pieces of the strap-like members are connected with each other by the catch, thereby keeping the wrist watch from falling off the arm.
For the catch, a buckle is mainly used in the case of the leather band and the plastic band while a connecting member called a clasp is often used in the case of the metal band.
The size of a user""s wrist portion varies from person to person due to differences in individuals. Accordingly, a wrist watch band is normally made up so as to be adjustable in length within a given scope of length.
For example, in the case of the leather band, one of the two pieces of strap-like members is provided with a plurality of holes opened in succession at intervals in the longitudinal direction, and the other one is provided with a positioning bar (buckle tongue) which is to be inserted into one of the holes described, disposed at a position such that a length of the leather band is fixed at an optimum length.
With the metal band, a length thereof is generally adjusted by increasing or decreasing the number of blocks, and when adjusting the length of the metal band, the blocks are disconnected from each other by extracting the adjust pin.
A conventional mechanism for adjusting the length of the wrist watch band using the blocks is described hereinafter with reference to FIGS. 25 and 26.
FIG. 25 is a perspective view showing an example of a wrist watch provided with a metal band made up of metal blocks connected with each other.
A wrist watch band 103 made of metal, attached to the wristwatch, comprises two braces 105, 106, each formed in a strap-like shape by arranging a plurality of blocks 102, made of a metal, in chain-shape, and by connecting the blocks 102 with each other by means of a connecting pin shown in FIG. 26, that is, an adjust pin 111.
The brace 106 is provided with a clasp 107 functioning as a connecting fixture at an open end thereof, and the clasp 107 is structured so as to connect the brace 106 with the brace 105.
With the wrist watch band 103, the number of the blocks 102 is increased or decreased by extracting and inserting the adjust pins 111 when adjusting the length thereof.
A mechanism for adjusting the length of the wrist watch band 103 by extracting and inserting the adjust pins 111 is described hereinafter with reference to FIG. 26.
For example, in the case of lengthening the wrist watch band 103, the adjust pin 111 in place at a portion of the wrist watch band 103, to be extended, is extracted, an additional block 102C is disposed between the blocks 102A and 102B, the adjust pin 111 is inserted into a connecting through-hole of a protrusion of the additional block 102C through a connecting through-hole 102a of the block 102A, and another adjust pin 111 passed through another connecting through-hole formed in the block 102C is inserted into a connecting through-hole 102c of a protrusion of the block 102B, thereby connecting the blocks 102A and 102C, and the blocks 102C and 102B, respectively.
On the contrary, in the case of shortening the wrist watch band 103, the adjust pins 111, 111, in place on both sides of a block which is to be removed, for example, the block 102C, are pulled out, and the block 102C is removed before connecting the blocks 102A and 102B again by means of the adjust pin 111.
When inserting the adjust pin 111 into the connecting through-holes of the blocks 102 to connect the adjoining blocks 102A and 102B to each other, the adjust pin 111 has to fit tightly into the connecting through-holes of the blocks 102 to prevent it from falling off after the insertion thereof.
However, a strong force required to fit the adjust pin into the respective blocks is contradictory to a necessity of extracting and inserting the adjust pin with ease when adjusting the length of the wrist watch band.
Consequently, since it has been impossible in the past to satisfy both needs at the same time, priority has been given to prevention of the adjust pin from falling off such that a fitting force required of the adjust pin is normally strengthened at the expense of ease with which the adjust pin is extracted. That is, the outside diameter of the adjust pin is designed at a size at which the adjust pin fits tightly (by large spring force as well as frictional force) into the connecting through-holes of the respective blocks.
As a result, inconvenience has been encountered in adjusting the length of the wrist watch band because the adjust pins can not be extracted and inserted with ease.
Meanwhile, there is available an adjust pin 121 of a split-pin type, as shown in FIG. 27. This adjust pin 121 is formed by folding back a metal wire semicircular in section such that a circular shape in section is formed as a whole by causing flat faces of the metal wire to be folded in half and to face each other. A curved section thereof is formed by causing a portion on both sides of the adjust pin 121, in the longitudinal direction, to swell outwardly, so that the ease with which the adjust pin 121 can be extracted out of a connecting through-hole 102a of a block 102, and reliability of the adjust pin 121 fitting into the connecting through-hole 102a can be obtained by the agency of elasticity of the curved section.
In general, an adjust pin of this type is manufactured by press working, but if material with a high restoring force is used for a constituent material of the adjust pin, press working can not be applied. Accordingly, the normal practice is to use material with a relatively low restoring force. Consequently, a fitting force of the curved section had to be designed on a stronger side at the expense, to a degree, of ease with which the adjust pin can be extracted from the block.
Further, in designing an outside diameter of an adjust pin of the split-pin type such as this, a bore of connecting through-holes of respective blocks into which the adjust pin is inserted, and a height of the curved section of the adjust pin, there have been needs of taking account of working fluctuation, wear and tear caused by extracting and inserting the adjust pin, and so forth. Accordingly, the bore of the connecting through-holes of the respective blocks have been often designed at a value on a fairly smaller side in a relative sense.
As a result, there have been times when it has become difficult to extract and insert the adjust pin and the adjust pin has undergone deformation when a fairly strong force is applied thereto to extract the adjust pin.
Further, the curved section is formed by simply folding back a metal wire semicircular in section in half so as to cause the flat faces of the metal wire folded to face each other, and is therefore susceptible to deformation. Consequently, due to deformation occurring to the curved section upon extracting and inserting the adjust pin, there has occurred misalignment of semicircular portions of the adjust pin at the juncture thereof, at one end (the upper end in FIG. 27) of the adjust pin.
With the adjust pin in such a state, the extraction force of the adjust pin has been drastically reduced, and in an extreme case, no fitting force at all has been developed, so that the adjust pin may have lost its function completely.
Further, the spring bar for purposes of connecting blocks of a wrist watch band with each other, formed of a shape-memory alloy (which has a superelastic property), has been described in Japanese Patent Laid-Open Publication No. 58-27505.
However, this spring bar is nothing but one in a shape with a pin-like piece protruded at both ends, formed of a shape memory alloy, and since no description has been made on that superelasticity is utilized for holding together blocks of a wrist watch band.
As described above, with all conventional adjust pins and wrist watch band connection structures, problems have been encountered. As priority has been given to the force required to fit the adjust pins into the respective blocks. Therefore the adjust pin could not be extracted or inserted with ease at times, or connection of band blocks with each other could not be ensured at times.
The present invention has been developed against such a technical background. One object of the invention is to provide an adjust pin capable of connecting a plurality of blocks together in the form of a chain with a certainty of fitting the pins into connecting through-holes formed in the blocks with a strong force, while enabling the insertion and extraction thereof to be executed with ease when adjusting the length of the wrist watch band, and a wrist watch band connection structure using the adjust pin.
Another object of the invention is to provide a method of manufacturing the adjust pin with ease.
To this end, the invention provides a wrist watch band adjust pin for connecting together a plurality of blocks of a wrist watch band made up of a plurality of blocks connected to each other in the form of a chain, wherein the adjust pin is formed of a metal with a property having a superelastic region where the stress remains constant against variation in strain, and provided with a curved section (bent part) formed at least at one spot thereof, for causing the stress in the superelastic region to act on adjoining blocks in a state wherein the adjoining blocks are connected to each other.
The adjust pin made up as described above, in a condition wherein the same is inserted in connecting through-holes formed in the adjoining blocks, is in a state of the bent part thereof pressing the inner wall face of the connecting through-holes, whereupon the adjust pin is securely held by a developed frictional force.
When the adjoining blocks are connected to each other by the adjust pin as stated above, a spring force acting on the inner wall face of the connecting through-holes becomes constant even if there is fluctuation in the bore of the connecting through-holes or the dimensions of the adjust pin, because a stress occurring on the bent part of the adjust pin remains within the superelastic region where the stress remains constant in spite of variation in strain.
Accordingly, without the need for designing in an advance fitting of the adjust pin into the connecting through-holes of the adjoining blocks in a tighter fashion to allow for working errors, and wear and tear, the adjust pin can be extracted out of and inserted into the connecting through-holes of the adjoining blocks with ease while stable fitting thereof can be effected.
The metal which has superelasticity, for use in the adjust pin is preferably an alloy composed mainly of nickel-titanium (NiTi) or nickel-titanium-cobalt (NiTiCo).
The bent part may be a portion of the adjust pin, bent into a bow shape, so that the bow portion can be fitted onto the inner wall face of the connecting through-holes formed in the adjoining blocks so as to be secured thereto. Further, the adjust pin is preferably provided with a curved surface formed by rounding both longitudinal ends into a semispheric shape.
In that case, even if the adjust pin has a property of high hardness, such a construction can prevent the tip of the adjust pin from shaving the inner wall face of the connecting through-holes when inserting the adjust pin into the connecting through-holes of the adjoining blocks.
Further, it is preferable that the adjust pin is in the range of 0.8 mm to 1.2 mm in wire diameter, and is provided with the bent part having a length in the range of 1 mm to 3.7 mm from a position thereof, on the side in contact with one of the adjoining blocks connected together, where the bent part starts bending, to a position thereof, at the maximum height (Hmax), along the horizontal direction.
The invention further provides a method of manufacturing the adjust pin, comprising steps of bending at least one spot of the wire made of a metal having a superelastic region by a press, cutting off the wire to a length so as to include a bent region thereof, and rendering both longitudinal ends of the wire a curved-surface shape.
The invention also provides a method of manufacturing the adjust pin, comprising steps of cutting off a wire made of a metal having a superelastic region to a desired length, bending at least one spot of the wire cut off by use of a press, and rendering both longitudinal ends of the wire a curved-surface shape.
The invention further provides a wrist watch band connection structure for connecting a plurality of blocks to each other in chain-like shape. Wherein the plurality of the blocks are each provided with a recess formed on one edge thereof in the direction of a chain of a wrist watch band, and a protrusion formed on the other edge thereof, on the opposite side, so as to be fitted into a recess of an adjoining block. And a connecting through-hole formed in a pair of arms of the blocks, separated by the recess, running along the direction of the width of the wrist watch band, respectively, and a connecting through-hole of a protrusion, provided in the protrusion, formed to run in the direction parallel with the connecting through-hole formed in the pair of the arms. And wherein by inserting the adjust pin made of a metal having a superelastic region where a stress remains constant against variation in strain into the connecting through-hole of the arms and the connecting through-hole of the protrusion, respectively, in a state wherein the protrusion of one of the blocks is fitted into the recess of another of the blocks, adjoining to the former, the blocks adjoining to each are detachably connected to each other.
That is, the wrist watch band connection structure is further constituted such that the adjust pin is provided with a bent part formed so as to have the maximum height thereof greater than the bore of the connecting through-hole formed in one of the pair of the arms. When the adjust pin is inserted up to a given position into the connecting through-hole formed in the pair of arms and the connecting through-hole of the protrusion, a stress occurring to the bent part of the adjust pin due to the bent part of the adjust pin undergoing flexure inside one of the connecting through-hole is designed to fall within the superelastic region, so that the adjust pin is secured to the adjoining blocks by a force of the stress.
An enlarged bored section is preferably formed at least on the inlet side of the connecting through-hole in one of the pair of the arms such that dimensions between the inner wall faces thereof, opposite to each other in the diametrical direction, is rendered larger than the diameter of the connecting through-hole of the protrusion.
Further, the enlarged bored section is preferably a stepped bored section formed at least on the inlet side of the connecting through-hole of one of the pair of the arms such that dimensions between inner wall faces thereof, opposite to each other in the diametrical direction, is rendered larger than the diameter of the connecting through-hole of the protrusion.
Furthermore, the enlarged bored section may be formed throughout the entire region of the connecting through-hole of one of the pair of the arms, and the connecting through-hole in one of the arms may be formed so as to have a bore such that, when the adjust pin is inserted up to a given position into the connecting through-hole formed in the pair of the arms and the connecting through-hole of the protrusion, a stress occurring to the bent part of the adjust pin due to the bent part of the adjust pin undergoing flexure inside the connecting through-hole formed in one of the arms falls within the superelastic region, enabling the adjust pin to be secured to the adjoining blocks by a force of the stress while the connecting through-hole in the other of the pair of the arms may be formed so as to have a bore slightly larger than the wire diameter of the adjust pin.
The adjust pin is preferably formed of an alloy composed mainly of nickel-titanium (NiTi) or nickel-titanium-cobalt (NiTiCo).
Further, it is preferable that the adjust pin of the wrist watch band connection structure also is in the range of 0.8 mm to 1.2 mm in wire diameter, and is provided with the bent part having a length in the range of 1 mm to 3.7 mm from a position thereof, on the side in contact with one of the adjoining blocks connected together, where the bent part starts bending, to a position thereof, at the maximum height (Hmax), along the horizontal direction.
Furthermore, with the wrist watch band connection structure, the bent part of the adjust pin is preferably formed by bending at a high temperature, or by applying heat treatment to the adjust pin after bending at a low temperature.